Biomedical Engineering Reference
In-Depth Information
DAQ
60 Hz Filter
Amplitude Measurement
Column Interpolation
*No. of Columns (N)
Row Insertion
*No. of Rows (M)
Finding Lump
Row Interpolation
Display Tactile Information
Figure 8.18
The flowchart of the algorithm implemented in LabVIEW and used for the graphical
rendering
For a graphical representation of a lump, two parameters had to be determined; firstly,
the location of the center of lump in each column and, secondly, its corresponding intensity
value. In order to designate the vertical location of the center of the lump in each column
(step 6, Figure 8.18), a relationship between the thickness of the tissue and the rows of
matrix was used. If a lump is located in the tissue at a distance from the upper sensor
array, it will be mapped onto row
r
, where
r
can be found from the relationship:
r
M
a
a
+
b
G
U
G
L
+
G
U
=
=
(8.13)
in which (
a+b
) is equal to the tissue thickness and considered to be proportional to
the number of rows. Regardless of whether or not a lump exists, the above equation was
applied to all columns (see Figure 8.20).
If a lump exists in a column, then
a
and
b
are the distances to the center of the lump
from the upper and lower sensor arrays, respectively. For the columns with no lump, the
associated sensor outputs are equal and
G
L
=
G
U
, thus
r
=
M
/2. These cells are indicated
in Figure 8.20 with a gray color. In other words, the algorithm assigns a nonzero value
to the middle row of the columns with no lump. Although this value is not significant, it
can be considered as a shortcoming of the algorithm.
In order to determine the intensity values of these locations in each column, the fol-
lowing relation was used:
G
rj
=
G
Uj
+
G
Lj
(8.14)
where index
G
rj
specifies the intensity value of the cell located in the row
r
and column
j
, showing the center of lump in that column. The result of this operation is a matrix, in
